Ultralow-dose, feedback imaging with laser-Compton X-ray and laser-Compton gamma ray sources

Patent metadata

Field	Value
Publication number	US-9983151-B2
Application number	US-201515320047-A
Country	US
Kind code	B2
Filing date	May 7, 2015
Priority date	May 8, 2014
Publication date	May 29, 2018
Grant date	May 29, 2018

Abstract

Ultralow-dose, x-ray or gamma-ray imaging is based on fast, electronic control of the output of a laser-Compton x-ray or gamma-ray source (LCXS or LCGS). X-ray or gamma-ray shadowgraphs are constructed one (or a few) pixel(s) at a time by monitoring the LCXS or LCGS beam energy required at each pixel of the object to achieve a threshold level of detectability at the detector. An example provides that once the threshold for detection is reached, an electronic or optical signal is sent to the LCXS/LCGS that enables a fast optical switch that diverts, either in space or time the laser pulses used to create Compton photons. In this way, one prevents the object from being exposed to any further Compton x-rays or gamma-rays until either the laser-Compton beam or the object are moved so that a new pixel location may be illumination.

First claim

I claim:

1. A method, comprising:
providing a beam from a laser Compton x-ray or gamma ray source;
directing said beam onto a first location of an object;
detecting, at a threshold of detection of a detector, a first portion of said beam that passes through said first location, to produce a first detected signal;
upon reaching said threshold of detection and producing said first detected signal, preventing said beam from propagating onto said first location;
determining a first number of photons or a first beam energy at said first location, wherein said first number of photons or said first beam energy is the amount required to produce said first detected signal at said threshold of detection;
directing said beam onto a second location of said object;
detecting, at said threshold of detection of said detector, a second portion of said beam that passes through said second location, to produce a second detected signal;
upon reaching said threshold of detection and producing said second detected signal, preventing said beam from propagating onto said second location;
determining a second number of photons or a second beam energy at said second location, wherein said second number of photons or said second beam energy is the amount required to produce said second detected signal at said threshold of detection; and
producing a map of the density of said object by spatially displaying (i) said first number of photons and said second number of photons, or (ii) said first beam energy and said second beam energy.

2. The method of claim 1 , wherein said first number of photons or said first beam energy required to reach said threshold of detection is determined by measuring the illumination time required by said beam to achieve said threshold of detection.

3. The method of claim 1 , wherein said beam is produced by a source that includes a linear accelerator for providing a series of bunches of relativistic electrons directed into an interaction region, wherein said source further comprises an interaction laser for providing a pulsed beam of laser light directed into said interaction region to collide with said electron bunches to produce said beam, wherein said beam is a quasi mono-energetic beam.

4. The method of claim 3 , wherein the step of preventing said beam from propagating onto said first location comprises diverting in space said pulsed beam of laser light from colliding with said electron bunches.

5. The method of claim 4 , wherein the step of preventing said beam from propagating onto said first location prevents said object from being exposed to said quasi mono-energetic beam any further until either said quasi mono-energetic beam or said object are moved so that a new location may be illuminated.

6. The method of claim 3 , wherein the step of preventing said beam from propagating onto said second location comprises diverting in time said pulsed beam of laser light from colliding with said electron bunches.

7. The method of claim 6 , wherein the step of preventing said beam from propagating onto said second location prevents said object from being exposed to said quasi mono-energetic beam any further until either said quasi mono-energetic beam or said object are moved so that a new location may be illuminated.

8. The method of claim 3 , wherein the steps of preventing said beam from propagating do not in any way perturb the steady state operation of said interaction laser or said accelerator and thus the beam available for exposure at each imaging location is identical from location to location during the steps of directing said beam.

9. The method of claim 1 , wherein said beam is a quasi mono-energetic beam that has a relative bandwidth of <20%.

10. The method of claim 1 , wherein said beam energy to reach said threshold is determined by measuring the illumination time required by the constant power source to achieve said threshold of detectability.

11. The method of claim 3 , wherein the step of preventing said beam from propagating onto said first location comprises diverting the seed laser pulse prior to amplification in the laser chain of said interaction laser.

12. The method of claim 3 , wherein the step of preventing said beam from propagating onto said first location comprises diverting the UV laser pulse that creates the electron bunches in said linear accelerator.

13. The method of claim 3 , wherein the step of preventing said beam from propagating onto said first location comprises mistiming the UV laser pulse that creates the electron bunches in the linear accelerator.

14. The method of claim 3 , wherein the step of preventing said beam from propagating onto said first location comprises mistiming the seed laser pulses for the laser amplification chain.

15. The method of claim 14 , wherein said seed laser pulses are mistimed with a delay that is of order the transit time of the laser and electron bunch through the interaction region.

16. The method of claim 3 , wherein the step of determining a first number of photons or a first beam energy comprises measuring the steady state electron beam parameters and then calibrating the x-ray or gamma-ray production as a function of the interaction laser beam energy.

17. The method of claim 3 , wherein the step of determining a first number of photons or a first beam energy comprises measuring the steady state electron beam parameters and then calibrating the x-ray or gamma-ray production as a function of the interaction laser beam energy, wherein the steady state electron beam parameters are measured by measuring the energy in a beam dump located after the interaction region or measuring current in a coil which is around the electron bunches.

18. The method of claim 1 , wherein the step of determining a first number of photons or a first beam energy comprises passing said beam through an aperture to remove a portion of photons, wherein the x-ray or gamma-ray energy deposited in this aperture is proportional to the total laser-Compton output and proportional to the on-axis flux used for the imaging, the step comprising determining the energy deposited in said aperture.

19. The method of claim 18 , wherein said aperture comprises scintillator material, wherein scintillation photons are measured and are a proportional measure of the total beam flux.

20. The method of claim 1 , wherein the step of determining a first number of photons or a first beam energy comprises passing the entire beam or just the off axis portion or just the on axis portion of the beam prior to illumination of the object through a standard ionization chamber used to measure x-ray or gamma-ray dose.

21. An apparatus, comprising:
a laser Compton x-ray or gamma ray source for providing a beam, wherein said source includes a linear accelerator for providing a series of bunches of relativistic electrons directed into an interaction region, wherein said source further comprises an interaction laser for providing a pulsed beam of laser light directed to collide with said electron bunches in said interaction region to produce said beam;
a detector configured to detect a portion of said beam after it passes through a location of an object;
means for determining the number of photons or a first beam energy at said location that were required to reach a threshold level of detectability by said detector;
means for preventing said beam from propagating onto said location when said detector detects, at said threshold level of detectability, a portion of said beam that passes through

Assignees

• L Livermore Nat Security Llc

Inventors

• Barty Christopher P J

Classifications

• G01N23/04 Primary

  and forming images of the material · CPC title

• G01N9/24

  by observing the transmission of wave or particle radiation through the material · CPC title

• H05G2/00 Primary

  Apparatus or processes specially adapted for producing X-rays, not involving X-ray tubes, e.g. involving generation of a plasma (X-ray lasers H01S4/00) · CPC title

• G01N2223/405

  mapping of a material property · CPC title

• A61B6/481

  involving the use of contrast agents · CPC title